1. Field of the Invention
The present invention relates to a superconducting device composed of a superconductor material and a semiconductor material and a method for manufacturing the same.
2. Description of Related Art
One example of a conventional superconducting device composed of a superconductor material and a semiconductor material has been proposed by T. Nishino et. al. in IEEE Transactions and Electron Devices Letters, Vol. 10 February 1989, page 61. The proposed superconducting device has been such that a switching operation is realized in a superconduction region (a also known as a spreading or permeating length, when spreading or penetrating into the semiconductor material from the superconductor material is realized. To this end, two superconductors are separated from each other by a distance corresponding to the above mentioned penetration length, and a space between the two superconductors is filled with a semiconductor, a carrier concentration of which is controlled by suitable means.
The carrier concentration in the semiconductor can be controlled by an electric field effect which can be realized by applying an electric field to the semiconductor, or by utilizing a PN junction. In both of these methods, a gate electrode can be provided on a semiconductor substrate surface on which superconductor electrodes are formed, or on a surface of semiconductor substrate opposite to the surface on which the superconductor electrodes are formed.
In the case of the conventional superconducting device, the penetration length of supeconduction condition is not greater than 0.1 .mu.m when a conventional semiconductor material is used. Therefore, when the gate electrode is provided on the same surface as the semiconductor substrate surface on which the superconductor electrodes are formed, it is necessary to form the gate electrode in a space of about 0.1 .mu.m between the superconductor electrodes. This is very difficult using current fine patterning technology.
If the gate electrode is provided on the surface of semiconductor substrate opposite to the surface on which the superconductor electrodes are formed, the planar structure required for integration of elements cannot be realized.